Fuel injection valve

ABSTRACT

A fuel injector for fuel injection systems of internal combustion engines includes a nozzle body. At a downstream end of the nozzle body at least one spray discharge opening is arranged. A sealing element is arranged on the nozzle body for sealing with respect to a contiguous component. At least one circumferential sealing ridge that forms a press fit with a contiguous component is arranged on the nozzle body as the sealing element.

FIELD OF THE INVENTION

The present invention relates to a fuel injector.

BACKGROUND INFORMATION

A fuel injector that includes a nozzle body which is tubular on itsdownstream side, and at whose downstream end a sealing seat and a spraydischarge opening are positioned, is described in German PublishedPatent Application No. 198 49 210. The tubular portion of the nozzlebody is insertable into a receiving bore of a cylinder head. The nozzlebody is sealed with respect to the receiving bore of the cylinder head,which has a diameter corresponding to the radial extension of the nozzlebody, with a seal that has approximately the geometry of a hollowcylinder.

For positional retention of the seal on the nozzle body, the nozzle bodyincludes a circumferential groove which is made, for example, by turningdown the nozzle body and into which the seal is inserted. Elasticmaterials that may be slid over the nozzle body for installation in thegroove may be used as materials.

A further fuel injector, in which a sealing element is positioned on thenozzle body, is described in German Published Patent Application No. 19808 068. The seal is made of a metallic material, and expands in theradial direction under the influence of the temperature created by thecombustion process. This may be implemented either by manner of ashape-memory alloy or the use of a bimetallic seal. A groove in thenozzle body may be used for retention, as in the case of GermanPublished Patent Application No. 198 49 210.

During operation of the internal combustion engine, the metal sealingring heats up and expands. The sealing effect is thus enhanced duringoperation. For easier assembly, the metal seal has a slightly smallerdiameter than the receiving bore that is introduced into the cylinderhead for the fuel injector.

A disadvantage of the sealing approach described in German PublishedPatent Application No. 198 49 210 is the high temperature acting on theseal. With direct-injection internal combustion engines, full-throttlestrength of nonmetallic seal materials may not be ensured.

The approach described in German Published Patent Application No. 198 08068 has the disadvantage that the sealing effect of the metallic seal istemperature-dependent. After a cold start of the internal combustionengine, it takes some time for the materials in the vicinity of thecombustion chamber to be heated by the combustion process sufficientlyto reach, by thermal conduction, a temperature in the seal that resultsin the requisite geometrical change. In addition to the seal described,a further seal is used in order to seal the combustion chamber withrespect to the exterior during initial operation of the internalcombustion engine, so that compression pressure is not lost.

The complex materials that are used in the manufacture of metallic sealswhich deform in temperature-dependent fashion are also disadvantageous.A shape-memory alloy has a transition temperature matched to theapplication. Close tolerances in the manufacturing process are useful inguaranteeing this transition temperature. The result is to increase notonly development costs for the alloy but also costs for utilization inseries production.

The use of a bimetallic seal requires retention of the seal on a nozzlebody, which serves as countermember upon deformation. Installation ofthe bimetallic element e.g. in a groove is difficult, however, since theproperties of the metals change if one of the two metals experiences aninelastic deformation during installation

SUMMARY OF THE INVENTION

The fuel injector according to the present invention may provide theadvantage that only a change in the geometry of the nozzle body resultsin sealing. Because the sealing ridges are configured in one piece withthe nozzle body, the seal is required to have a sealing function onlywith regard to the contiguous component. Another consequence is that nomaterials that may be damaged as a result of the temperatures that occurare used in the immediate vicinity of the combustion chamber. The purelymetallic seal is a constituent of a component that is used in any case,so that furthermore no additional corrosion protection (for example, dueto possible contact corrosion) is necessary.

The one-piece configuration reduces the production complexity of thefuel injector, and moreover ensures low rejection rates because oneassembly step may be omitted.

The successive positioning of multiple sealing ridges may beadvantageous especially in terms of the reliability of the sealingeffect. The identical geometry of the individual enlargements simplifiesmanufacture, so that tool costs may be reduced.

It may be additionally advantageous that an increase in the number ofsealing elements does not result in an increase in the number ofcomponents of the fuel injector. The sealing ridges may be machined indifferent quantities out of the same nozzle body blank.

The use of an adapter sleeve as contiguous component may allow thesealing of the unit comprising the fuel injector plus adapter sleevewith respect to the cylinder head to be shifted to a location that isless critical in terms of temperature.

An example embodiment of a fuel injector according to the presentinvention is depicted in the drawings and is explained in thedescription below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic partial section through an example embodiment of afuel injector according to the present invention.

FIG. 2 is a schematic section, in portion II of FIG. 1, through the fuelinjector according to the present invention.

DETAILED DESCRIPTION

For better comprehension of the present invention, an example embodimentof a fuel injector 1 according to the present invention will first beexplained briefly with reference to FIG. 1 in an overall presentation interms of its constituents.

Fuel injector 1 is embodied in the form of a fuel injector 1 for fuelinjection systems of mixture-compressing, sparkignited internalcombustion engines. Fuel injector 1 is suitable for direct injection offuel into a combustion chamber (not depicted) of an internal combustionengine.

Fuel injector 1 includes a nozzle body 2 in which a valve needle 3 ispositioned. Valve needle 3 is in working engagement with a valve closureelement valve-closure member which coacts with a valve-seat surface 6,positioned on a valve seat element 5, to form a sealing seat. In theexample embodiment, fuel injector 1 is an electromagnetically actuatedfuel injector 1 that possesses at least one spray discharge opening 7.Nozzle body 2 is sealed by a seal 8 with respect to an external pole 9of a magnet coil 10. Magnet coil 10 is encapsulated in a coil housing 11and wound onto a coil support 12 that rests against an internal pole 13of magnet coil 10. Internal pole 13 and external pole 9 are separatedfrom one another by a gap 26, and are supported on a connectingcomponent 29. Magnet coil 10 is energized, via a conductor 19, by anelectrical current that may be conveyed via an electrical plug contact17. Plug contact 17 is surrounded by a plastic sheath 18 that may beinjection-molded onto internal pole 13.

Valve needle 3 is guided in a valve needle guide 14 that is ofdisk-shaped configuration. Paired with the latter is an adjusting disk15 that serves to adjust the valve needle stroke. Located on theupstream side of adjusting disk 15 is an armature 20. The latter isjoined nonpositively, via a flange 21, to valve needle 3, which isjoined to flange 21 by manner of a weld seam 22. Braced against flange21 is a return spring 23 which, in the present configuration of fuelinjector 1, is preloaded by a sleeve 24 pressed into internal pole 13.

Fuel conduits 30 a through 30 c extend in valve needle guide 14, inarmature 20, and in a guidance disk 31. A filter element 25 ispositioned in a central fuel inlet 16. Fuel injector 1 is sealed withrespect to a fuel line (not depicted) by manner of a seal 28.

When fuel injector 1 is in the idle state, armature 20 is impinged uponopposite to its linear stroke direction, via flange 21 on valve needle3, by return spring 23, so that valve-closure member 4 is held insealing contact on valve seat 6. Upon energization of magnet coil 10,the latter establishes a magnetic field that moves armature 20 in thelinear stroke direction against the spring force of return spring 23,the linear stroke is defined by a working gap 27 that is present, in theidle position, between internal pole 13 and armature 20. Armature 20also entrains flange 21, which is welded to valve needle 3, in thelinear stroke direction. Valve-closure member 4 lifts off fromvalve-seat surface 6, and fuel is discharged from spray dischargeopening 7.

When the coil current is shut off and once the magnetic field hasdecayed sufficiently, armature 20 falls away from internal pole 13 ontoflange 21 as a result of the pressure of return spring 23, therebymoving valve needle 3 against the linear stroke direction. Valve-closuremember 4 is thereby placed onto valve-seat surface 6, and fuel injector1 is closed.

Fuel injector 1 according to the present invention is sealed withrespect to an adapter sleeve 32 by manner of at least one sealing ridge31 that is positioned as a radial enlargement on nozzle body 2. Insteadof adapter sleeve 32 depicted in the example embodiment, any contiguouscomponent may be used. Adapter sleeve 32 may allow fuel injectors 1 tobe installed into a cylinder head that would require changes to theoutside dimensions of fuel injector 1. Adapter sleeve 32 includes at itsdownstream end a tubular part 35, the inner radial extension of tubularpart 35 corresponding to the outer radial extension of nozzle body 2.Tubular part 35 has a cylindrical inner contour. Adapter sleeve 32 issealed with respect to the cylinder head in a manner that is notdepicted.

The length of tubular part 35 of adapter sleeve 32 is at leastsufficient that all the sealing ridges 31 provided for sealing of nozzlebody 2 together include a smaller extension in the axial direction thantubular part 35 of adapter sleeve 32, and thus are positioned withintubular part 35. Sealing ridges 31, which are positionedcircumferentially around cylindrical nozzle body 2 as radially enlargedregions, include an outer radial extension which is somewhat greaterthan the inner radial extension of tubular part 35 of adapter sleeve 32.When nozzle body 2 is inserted into adapter sleeve 32, a press-fit joinwhich assumes the sealing function is thus produced between nozzle body2 and adapter sleeve 32. Since adapter sleeve 32 is in turn sealed (in amanner not depicted) with respect to the cylinder head, it is notpossible for the pressure in the combustion chamber (not depicted) toescape into its surroundings.

Nozzle body 2 is of cylindrical configuration, its outer radialextension (especially downstream of sealing ridges 31) is somewhatsmaller than the outer radial extension of sealing ridges 31. Thecontact area between nozzle body 2 and adapter sleeve 32 is therebylimited to sealing ridges 31. The surface pressure resulting from thepress-fit join and the small contact area ensures the sealing effect.Sealing ridges 31 positioned successively in the axial direction haveidentical cross sections.

Instead of adapter sleeve 32, fuel injector 1 may also be installeddirectly into a cylinder head of a direct-injection internal combustionengine. For that purpose, the cylinder head includes a receiving orificefor fuel injector 1 that corresponds, at least in a subregion, to thegeometry of adapter sleeve 32, so that when fuel injector 1 is in theinstalled position, sealing ridges 31 of nozzle body 2 seal fuelinjector 1 with respect to the receiving orifice of the cylinder head.As an alternative to the identical geometry of the individual sealingridges 31 in the example embodiment depicted, sealing ridges 31 may alsobe embodied with differing cross sections.

FIG. 2 is an enlarged depiction of the sealing portion of nozzle body 2shown in FIG. 1. Sealing ridges 31 constitute the only contact areasbetween nozzle body 2 and adapter sleeve 31, and thus generate thesealing surface pressure. Upstream and downstream from sealing ridges31, an air gap 34 is formed as a result of the smaller radial extensionof nozzle body 2 as compared to the inner radial extension of adaptersleeve 32.

External radii 33 of sealing ridges 31 in the region of the contactsurface against adapter sleeve 32 are selected to be sufficiently largethat chips may not be shaved off from adapter sleeve 32 upon assembly.Chip-free assembly is especially important in the context of directinstallation into a cylinder head, since the metal chips would falldirectly into the combustion chamber.

1. A fuel injector for a fuel injection system of an internal combustionengine, comprising: a nozzle body that includes at least one spraydischarge opening arranged at a downstream end of the nozzle body; acontiguous component; and a sealing element configured to seal withrespect to the contiguous component; wherein the sealing elementincludes at least one circumferential sealing ridge that forms a pressfit with the contiguous component; and wherein the nozzle body andsealing element are formed as a one-piece configuration and the sealingridge is an integral radial enlargement of the downstream end of thenozzle body.
 2. The fuel injector according to claim 1, wherein: the atleast one circumferential sealing ridge includes a plurality of sealingridges arranged successively in an axial direction on the nozzle body.3. The fuel injector according to claim 2, wherein: the plurality ofsealing ridges have an identical geometry.
 4. The fuel injectoraccording to claim 1, wherein: the nozzle body, at least in a region ofthe at least one circumferential sealing ridge, is cylindrical as far asthe downstream end.
 5. The fuel injector according to claim 1, wherein:the fuel injector is insertable with the downstream end of the nozzlebody into the contiguous component.
 6. The fuel injector according toclaim 1, wherein: the contiguous component includes an adapter sleevethat is slidable onto the fuel injector.
 7. The fuel injector accordingto claim 1, further including an air gap on both a downstream andupstream side of each of the at least one sealing ridges between asurface of the contiguous component and a surface of the downstream endof the nozzle body.